1. Field of the Invention
This invention relates to a process of plastics waste sortation, and more particularly addresses separation of the multiple plastics and non-plastics constituents found in soda beverage bottles namely polyethylene (PE), polyethylene terephthalate (PET); Aluminum (Al), labels and adhesives.
2. Description of the Prior Art
The perennial garbage pile-up has emerged as one of the most frustrating national problems. And, plastics today are squarely at the very core of the current solid waste debate. A serious challenge confronts the U.S.: appropriate disposal of 320 billion lbs. of waste that pours annually into municipal solid waste streams to be buried, burned or less often recycled. Recycling, although not inexpensive in itself, can be less costly than other disposal methods because their is both a return on the reused material and an offset on the landfill charges. Moreover, increasing prices of virgin plastics, the limited reserves of natural resources such as petroleum, stringent environmental regulations and skyrocketing tipping fees have made recycling imperative as well as economically attractive.
Salvaging plastics from domestic waste poses quite a problem technically because of the heterogeneity of the wastes. The soda beverage bottle provides a classic recycling history. Most commercial PET bottle recovery processes currently employed, appear to be a version of the basic PET bottle recycling process embodied in the CPRR process (Center for Plastics Recycling Research at Rutgers University in Piscataway, N.J.).
PET beverage bottles are not one but several materials: a PET body (clear or green), a pigmented high density polyethylene (HDPE) base cup, aluminum (Al) cap, labels and adhesives. A typical method for separation of these components developed by CPRR (Ref.: Modern Plastics Supplement, "Waste Solutions", April 1990, p 32-35) is described hereinafter. In this process the bottles are shredded and ground into chips. The chips are then air classified to remove the light weight paper and other contaminants. To remove the labels still attached to the chips, the granulated mixture undergoes a detergent wash. Once the labels and adhesives are removed, the lighter HDPE fraction is separated from the heavier PET and aluminum pieces by flotation methods (some of the process technologies use a hydrocyclone system at this point). The HDPE chips are then dried and collected. PET and aluminum mixture goes on for final separation.
The PET and aluminum chips require further drying so that they can be electrostatically separated. This is the most expensive part of the process (Ref: Chemical and Engineering News, Jan. 30, 1989, p. 11).
These prior art processes suffer from several disadvantages which make then economically unattractive. Wet operations of necessity require large amounts of water. Intermediate drying steps to enhance the efficiency of PET/metal separation are costly. The electrostatic separation step for PET/Aluminum mixture is a major financial hurdle for economic reclamation of bottle constituents.
With the knowledge of the prior art and its shortcomings it can be readily inferred that there is a need for a beverage bottle recovery process, which:
(1) can economically separate the constituent plastics and non-plastics in a soda beverage bottle, PA0 (2) does not require expensive electrostatic separation techniques for recovery of aluminum, PA0 (3) does not involve multiple separation steps.
These needs are adequately satisfied by the process of the current invention.